os: fix get_raw_line for EOF on OpenBSD (fix #26361) (#26368)

Author: lcheylus

vlib/os/os.c.v

@@ -615,8 +615,21 @@ pub fn get_raw_line() string {
 	} $else {
 		max := usize(0)
 		buf := &u8(unsafe { nil })
+
+		mut str := ''
 		nr_chars := unsafe { C.getline(voidptr(&buf), &max, C.stdin) }
-		str := unsafe { tos(buf, if nr_chars < 0 { 0 } else { nr_chars }) }
+		// On OpenBSD, buf=0 for EOF =>  panic when calling tos function
+		$if openbsd {
+			if nr_chars != -1 {
+				str = unsafe { tos(buf, nr_chars) }
+			} else {
+				if int(C.feof(C.stdin)) == 0 && int(C.ferror(C.stdin)) != 0 {
+					panic('get_raw_line(): error to read string')
+				}
+			}
+		} $else {
+			str = unsafe { tos(buf, if nr_chars < 0 { 0 } else { nr_chars }) }
+		}
 		ret := str.clone()
 		$if !autofree {
 			unsafe {